The major objective of this project is to study chemical effects on differentiation as well as to investigate the biochemical and genetic mechanisms involved in early development and implantation. Areas of current interest include: (1) the determination of the role, fate, and the degree of cellular interaction of known transplanted single cell(s) in the development of host embryo; (2) the relationship of concentration and period of exposure to selected agents which induce embryopathy; and (3) the characterization of basic biochemical, physiologic, and genetic damage in vitro and in vivo.